Piers
Well-Known Member
With all the recent talk about fuel consumption, I'm wondering about fitting fuel flow meters to Play d'eau. Where do I start looking for such items?
Cummins 450c Fuel Flow
- Thread starter Piers
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Bouba
Well-Known Member
Piers, don’t you have SmartCraft or Vessel View?
Piers
Well-Known Member
No - please tell me more.
superheat6k
Well-Known Member
If you have electronically controlled engines then the fuel flow of fuel being burnt might be available to view.
If you do wish to consider using flow metering the Floscan are the units to look at, but there are some significant problems with accurate flow measurement on a system with variable flow and separately variable return, further complicated by variable viscosity if the fluid.
On a diesel consumption is fuel flow to less spill return, and both are subject to separate variations. This means a small measuring error in the flow to can be compounded by another error in the spill return, and these errors themselves could vary with fuel temperature and hence viscosity.
A 5% metering error could compound to as high as a 25% overall error, whereas to be of reliable use the metering as a whole would need to achieve better than 10% accuracy IMHO.
I did look into meters but I felt the cost and likely inaccuracy was not worth pursuing.
If you do wish to consider using flow metering the Floscan are the units to look at, but there are some significant problems with accurate flow measurement on a system with variable flow and separately variable return, further complicated by variable viscosity if the fluid.
On a diesel consumption is fuel flow to less spill return, and both are subject to separate variations. This means a small measuring error in the flow to can be compounded by another error in the spill return, and these errors themselves could vary with fuel temperature and hence viscosity.
A 5% metering error could compound to as high as a 25% overall error, whereas to be of reliable use the metering as a whole would need to achieve better than 10% accuracy IMHO.
I did look into meters but I felt the cost and likely inaccuracy was not worth pursuing.
Bouba
Well-Known Member
These are Cummins electronic instruments for measuring everything in your engine. For example my tacho is a SmartCraft and below the analog display is a digital readout line that has many functions including fuel consumption. The Vessel View is a separate screen that monitors the health of the engine. They are for electronic controlled engines but date all the way back to 2000
https://www.sbmar.com/articles/which-cummins-smartcraft-display-do-i-have/
Piers
Well-Known Member
Play d'eau's engines are not electronically controlled (thankfully), so if there's likely to be up to 25% inaccuracy it's a pretty pointless exercise. Thank for the info.
Bouba
Well-Known Member
I guess that rules out SmartCraft
MapisM
Well-Known Member
IIRC, the 450 has a mechanical rather than electronic governor (as the 480 has).
And IF I'm correct, there's nowhere a computerized trick like the SC or VV can get the necessary data from, and the only way to measure fuel burnt is through flow sensors on both lines, as explained by SH6K.
Apropos, SH6K, I am also considering the Floscan thingie, because I always heard nothing but praises about them and their reliability (in fact, I would have probably fitted them already, if it weren't a bit in doubt about whether they are really worth the cost, in a boat which will never be used for very long passages anyway).
I'm surprised to hear of a potential 25% error, 'cause afaik their accuracy is MUCH higher. R U sure about that?
PS: doh!
Sorry, I began writing this post before the last three were published, then I got a phone call and eventually published mine...
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Piers
Well-Known Member
I'll have a chat with Floscan and let you know the outcome. It sounds like a lot of engineering work will need to be carried out, though.
superheat6k
Well-Known Member
I did the maths on this on here a few years ago, but happy to do the sums again. This might take a while, so bear with me.IIRC, the 450 has a mechanical rather than electronic governor (as the 480 has).
And IF I'm correct, there's nowhere a computerized trick like the SC or VV can get the necessary data from, and the only way to measure fuel burnt is through flow sensors on both lines, as explained by SH6K.
Apropos, SH6K, I am also considering the Floscan thingie, because I always heard nothing but praises about them and their reliability (in fact, I would have probably fitted them already, if it weren't a bit in doubt about whether they are really worth the cost, in a boat which will never be used for very long passages anyway).
I'm surprised to hear of a potential 25% error, 'cause afaik their accuracy is MUCH higher. R U sure about that?
PS: doh!
Sorry, I began writing this post before the last three were published, then I got a phone call and eventually published mine...
MapisM
Well-Known Member
Well, of course the installation takes much more time than just plugging an additional instrument on an already available socket.
But if your fuel lines are easily accessible (and I suppose they are on your boat, as well as on my DP), it's essentially a matter of fitting the small flow measuring section anywhere along both lines (for each engine - i.e. 4 in total).
The other thing is snaking the cables from the e/r up to the p/h.
Otoh, if the measurement is as reliable as I was thinking before reading SH6K post (i.e. within 5% MAX), it's very nice to have the MPG in real time - which Floscan can provide by simply connecting their gauge to a NMEA GPS signal, and which normally you don't have even with the more modern displays of electronically controlled engines (unless fitted with additional interfaces, like the Maretron stuff).
rustybarge
Well-Known Member
Surprisingly enough the electronic data for common rail injection diesels is very inaccurate , as can be seen from the misleading mpg in the car world with Ford and VW originally quoting 80+mpg for some of their models, which owners reported as 50-55mpg in real life.
The reason is multi sequential injectors which separately squirt into the cylinders 3 or 4 tiny amounts of fuel on each piston stroke: virtually impossible to measure acturately when we are talking about micro volumes of liquid over minute micro fractions of seconds .
A lot of long distance trawlers have day tanks so that the skipper can monitor the hourly fuel consumtion which takes into consideration the sea conditions at that moment in time. A 3' head sea could increase fuel consumption by 30%, and what about a following wind or a tidal race?
Its relatively easy to install a couple of tee-piece connectors before the fuel filter with a simple 2 way valve. A electric pump will fill the day tank in the pilot house .....probably much cheaper than an electronic gizmo.
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MapisM
Well-Known Member
Thanks in advance, I for one am interested to check that out! :encouragement:
MapisM
Well-Known Member
LOL, it's installing a day tank if you don't have one, that is neither easy nor cheap!
Btw, I'm of course more than happy to stand corrected by Piers, but even if it's been a while since I saw a Flem 55 e/r, if I should bet on her having a day tank or not, I'd rather put my money on the latter.
Regardless, day tanks are practically unknown to 99% of pleasure boats.
PS: ref. inaccuracy of fuel consumption data in cars, I believe it's just down to ideal vs. real life conditions, not to any technical difficulties in the calculation.
There's no reason why the electronic numbers should be inaccurate, because they are not based on any sort of flow measurement.
The numbers are simply taken from the ECU: whatever the ECU "decides" to send to the injectors is translated in the numbers you can see on your dash - straight from the horse's mouth, so to speak.
The only reason for relevant differences can be due to malfunctioning, like for instance a defective injector (which is a very are occurrence anyhow, nowadays).
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Piers
Well-Known Member
No day tank, just four separate tanks, each able to supply each engine, with the selected engine delivering its overspill back to the selected supply tank.
Looking at the Flowscan instrumets, they all seem to have RPM and other readouts, when all I want is a good looking meter to show me fuel burn in ltrs/hr.
MapisM
Well-Known Member
Happy to hear that my memory still gives me some momentary glimpes of reason...
Back to what RB suggested, the fact that not even Fleming has a day tank goes a long way in explaining how hardly applicable your idea is, I'm afraid.
Ref.Floscans, the digital models also show the RPM, and on top of L/hr (which they can indeed show), they can also calculate L/Nm in real time, as I said - which is handy for calibrating the optimal cruising speed.
And having also RPM means that you could fit the Floscan instrument where you currently have the RPM-only gauge, which is also nice, imho.
Then again, IIRC they still sell also the simpler analogue-only version, only capable to show L/hr (in the EU version, or gallons in the US version).
Piers
Well-Known Member
I suspect L/nm will come from using GPS which will give L/nm over the ground which will vary considerably given tidal flow. I'd prefer to use the log output so I'd have L/nm through the water. But apart from this, just L/hr on its own would be fine. I wouldn't want to change the Fleming instrument panel, so separate insts would be OK.
This discussion is getting better by the hour. Really good.
rustybarge
Well-Known Member
We had a Genny on the farm which had a 50gal day tank which was fed off a big bulk tank of diesel : its very comforting to know your exact consumtion every day.
The physical inspection of the level leaves no doubt...
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Portofino
Well-Known Member
What I have discovered recently on my Lorenz plotter is a time to destination functionality .
So along with the L/ Hr on the MAN screens , I can see how much the trip will use .
A bit of real mental maths work out the € cost .
It’s quite funny really , Because instinct says the slower the less fuel burn , Ok we all agree in absolute terms ) except when getting over the hump in a P Boat ) — but in reality once up and planing , there’s a flat ness on one graph. So from. €€€ cost wise , it makes hardly any difference , wether we go 22 or 32 knots , you just get there quicker , doing 32 , but the overall cost is the same cos the higher burn rate is less time .
Hence my recent preferences to bin D or slow P , — and run about at 80 % or there abouts load .
Any perceived fuel saving ( actually cost ) benefit of running a P boat slower is just that “ perception “
So along with the L/ Hr on the MAN screens , I can see how much the trip will use .
A bit of real mental maths work out the € cost .
It’s quite funny really , Because instinct says the slower the less fuel burn , Ok we all agree in absolute terms ) except when getting over the hump in a P Boat ) — but in reality once up and planing , there’s a flat ness on one graph. So from. €€€ cost wise , it makes hardly any difference , wether we go 22 or 32 knots , you just get there quicker , doing 32 , but the overall cost is the same cos the higher burn rate is less time .
Hence my recent preferences to bin D or slow P , — and run about at 80 % or there abouts load .
Any perceived fuel saving ( actually cost ) benefit of running a P boat slower is just that “ perception “
Portofino
Well-Known Member
We have sight glasses with incremental marks .
I,am often surprised — see post ^^^ — of how little fuel we have used sometimes , or turning it arround. How long it lasts
